As an index for a refinement and an alteration (degradation) of edible oil and fat, total polar materials (referred hereafter as “TPM value”), an acid value (referred hereafter as “AV value”), etc. are used.
The TPM value uses an amount of total polar materials (TPM), which is a generic name of a free fatty acid that is generated by moistures in food (deep-fried food), an aromatic compound that is increased by heating, and a material that is produced by oxidation due to contact with air, etc., as an index. This TPM value can be derived from a measurement result of a dielectric constant of oil/fat.
The AV value is defined by an amount (mg) of kalium hydroxide (KOH) that is required in neutralizing free fatty acids existing in 1 g of edible oil and fat.
Note that the TPM value is used as an index in Europe, whereas the AV value is used as an index in Japan.